1. Field
The presently disclosed subject matter relates to an LED light source and a manufacturing method for the LED light source, and more particularly to a reliable LED light source that can provide a favorable light distribution for a vehicle headlight and the like and a method for manufacturing the LED light source.
2. Description of the Related Art
Recently, various LED chips have been used as a light source for—vehicle lamps resulting in improved brightness. When an LED light source using the LED chips is used for a vehicle headlight and the like, the LED light source is frequency constructed by mounting the LED chips on a circuit board so that the circuit board can be attached to a reflector and the like of the vehicle headlight.
Such an LED light source and a vehicle headlight using the LED light source are disclosed in patent document No. 1 (Japanese Patent Application Laid Open JP2005-32661). FIG. 13 is a conventional LED light source for a vehicle headlight, which is disclosed in patent document No. 1. The conventional LED light source includes: a circuit board 51; an LED chip 50 mounted on the circuit board 51; bonding wires 53 electrically connecting electrodes of the LED chip 50 to conductor patterns of the circuit board 51; and a reflector attached to the circuit board 51 so as to cover the LED chip 50.
Therefore, when providing the electrodes of the LED chip 50 with a power supply from an external battery via the conductor patterns of the circuit board 51, the conventional LED light source can illuminate light emitted from the LED chip 50 in a direction toward the arrow shown via the reflector 52. A heat sink may be located adjacent to the circuit board in order to radiate heat generated from the LED chip 50 away from the circuit board and the LED chip 50.
The LED chip 50 is frequency mounted on the circuit board 51 via a sub mount substrate due to various reasons such as an improvement of workability, an increase of the radiating efficiency, etc. FIG. 14 is a perspective view showing another conventional LED light source using the sub mount substrate, which is disclosed in patent document No. 1.
The other conventional LED light source includes: the circuit board 51; the LED chip 50 mounted on a sub mount substrate 61 that is mounted on the circuit board 51; metal blocks 62 mounted on the conductor patterns of the circuit board 51, the bonding wires 53 electrically connecting each of electrodes of the LED chip 50 to the respective metal blocks 62; and a protection element 63 such as a zener diode and the like connected between the metal blocks 62, that is, between the electrodes of the LED chip 50.
In the above-described conventional LED light sources, the bonding wires 53 are not protected from external pressure. Accordingly, in manufacturing processes that occur after the wire bonding process (e.g. a process for attaching the reflector 52 to the circuit board 51 including the bonding wires 53), problems such as the bonding wires 53 disconnecting or shorting may be caused by the external pressure.
As a first countermeasure for the above-described problems, a structure in which an encapsulating resin encapsulates the LED chip including the bonding wires therewith is disclosed in patent document No. 2 (Japanese Patent Application Laid Open JP2007-329068), etc. As a second countermeasure, a structure in which a dome-shaped transparent lens covers the LED chip including the bonding wires along with the circuit board is disclosed in patent document No. 3 (Japanese Patent Application Laid Open JP2009-054633), etc.
The above-referenced Patent Documents are listed below and are hereby incorporated with their English abstract in their entirety.    1. Patent document No. 1: Japanese Patent Application Laid Open JP2005-32661    2. Patent document No. 2: Japanese Patent Application Laid Open JP2007-329068 (U.S. patent application Ser. No. 11/759,482)    3. Patent document No. 3: Japanese Patent Application Laid Open JP2009-054633 (U.S. patent application Ser. No. 12/198,098)
However, in a structure including an encapsulating resin, the encapsulating resin may alternate between expansion and a contraction due to a heat cycle, which is caused by alternating on and off states of the LED chip. The thermal stress of the expanse and the contraction may cause problems such that the bonding wires weaken.
In addition, in the structure including the dome-shaped transparent lens, a part of light emitted from the LED chip may be absorbed by the dome-shaped transparent lens. Accordingly, the transparent lens may cause a reduction in light use efficiency of the LED light source.
The disclosed subject matter has been devised to consider the above and other problems, characteristics and features. Thus, an embodiment of the disclosed subject matter can include a reliable LED light source in which bonding wires can be protected from external pressure. In this case, the bonding wires can be protected by a structure that does not include an encapsulating resin and a dome-shaped lens while the number of the bonding wires is reduced by using a flip type LED chip even if the number of the LED chips increases. Thus, the LED light source can result in high reliability and a favorable light distribution, and therefore can be employed for various lighting units such as a vehicle headlight, general lighting, etc.